Bridge construction



March 28, 1939. sc u-rz 2,152,069

BRIDGE CONSTRUCTION Filed Sept. 13, 1937 if W Patented Mar. 28, 1939 UNITED STATES BRIDGE CONSTRUCTION Myron I. Lifschutz, Chicago, Ill.

Application September 1 v 1 Claim.

This invention relates to artificial teeth and particularly to improvements in porcelain occlusal facings for molars and bicuspids in sanitary bridge work, and for short bite removable bridges where there is not sufficient space for full sized teeth.

Sanitary bridges are usually constructed in lower posterior restorations of bicuspids and molars after absorption of the gum ridge has progressed to a considerable extent. A bridge of this type consists of an occlusal platform or base attached to abutment crowns or inlays and the buccal and lingual surfaces of the platform or base are rounded downwardly and inwardly to provide a more or less convex bottom surface. lChe purpose of this construction is to preserve as much space as is possible between the gum ridge and the bridge structure, so that food will not lodge underneath the bridge.

At present this class of dental Work is being mainly constructed Wholly of metal as the use of porcelain in sanitary or. hort bite removal bridge work has not heretofore proved to be practical. Metal, however, is objectionable from an anesthetic viewpoint, as most people have an aversion to the appearance of any sort of metal in the mouth.

The main objects of this invention are to provide an improved porcelain facing that will simulate the appearance of a natural tooth and reduce the amount of metal used in sanitary bridge construction; to provide an improved porcelain occlusal facing for bridge work having an improved arrangement of interlocking means between the facing and the supporting metal structure; to provide such a facing arranged to provide greatest strength at the point where needed while permitting less mass or bulk than porcelain facings heretofore employed; to provide an improved porcelain occlusal facing that may be of substantially standard form suitable for mass commercial production; to provide an improved removable occlusal facing; to provide an improved porcelain facing and supporting bridge construction requiring considerably less metal than is ordinarily employed in bridge constructions; and to provide an improved preformed metal backing member that may be standardized to simplify bridge work construction.

A specific embodiment of this invention is shown in the accompanying drawing in which:

Fig. 1 is a view showing the improved bridge structure mounted on the teeth of a lower jaw,

-- the teeth being shown in dotted outline.

3, 1937, Serial No. 163,643

Fig. 2 is a view of the improved porcelain occlusal facing for a molar.

' Fig. 3 is a buccal or lingual view of the same.

Fig. 4 is a mesial or distal view of the same.

Fig. 5 is a perspective view of an improved 5" metal partial-backing member Fig. 6 is a sectional view of line 6-6 of Fig. 5.

Fig. 7 is a sectional view of the same taken on line l-'l of Fig. 5.

Fig. 8 is a sectional view of an assembled complete backing member and occlusal facing as taken on line 8-8 of Fig. 1 and showing in dotted outline the position of the occlusal facing as it is being fit into the backing member.

Fig. 9 is a sectional view of a sanitary bridge construction embodying the improved backing and occlusal facing.

Fig. 10 is a sectional view of a mold showing the mannerin which the partial backing member 20 is positioned and made ready for the casting of a complete backing, and

Fig. 11 is a sectional view of the same after the casting, showing how the preformed backing member becomes an integral part of the com- 25 pleted backing.

As shown in the drawing, the improved occlusal facing I is a relatively shallow solid body made of porcelain or other suitable material simulating natural teeth, and particularly designed for mo- 30- lars or bicuspids in dental restorations. The top or occlusal surface of the facing is preferably anatomically carved for articulation with opposing teeth and the mesial-distal, lingual and buccal margins are rounded so as to smoothly blend into the supporting bridge structure. The base 2 of the improved facing is substantially convex in both mesio-distal and bucco-lingual direction, and on this convex base the same taken on a convex dove-tailed mounting lug 3 running 42)" bucco-lingually is provided.

The buccal end 4 of the lug 3 is preferably wider than the lingual end 5 of the same, so that the lug narrows as it approaches the lingual side of the facing, and as shown in Fig. 3, the 45'v sides of the lug 3 are undercut as at 6 so that the lug will be vertically dove-tailed toward the convex base for the purpose of interlocking with the metal supporting structure. The corner formed by undercut or groove 6 is curved in the vertical plane parallel with the lug 3 to conform with the rounded or convex base of the facing. The lug 3 is located substantially midway between the mesial and distal margins of the base surface 2, and due to its convexity the lug 3 has downwardly and inwardly, 35-

its greatest depth at the center of the facing. Thus, the convexity of the base 2 of the facing and the location of the lug, provide the greatest strength directly beneath the portion of the occlusal surface wherein the grooves or fissures that are provided to simulate the natural occlusal surface are the deepest. In this manner a facing of great strength is provided, While the mass or bulk of the facing is kept at a minimum by being thinned toward the margins in the formation of the convex base 2.

The convex lug 3' by having its greatest depth at the center of the facing also permits the supporting bridge structure to take a form wherein its greatest depth or thickness will be at its middle allowing immediate thinning toward the buccal and lingual margins, so as to provide the ideal sanitary shape and construction.

As shown in Fig. 8, the facing I is held in a shallow cup-shaped cast metal supporting structure preferably of gold which is connected to an abutment, comprising a crown portion or an inlay, on each side for attachment to existing teeth according to the usual practice for bridge work. This cup-shaped supporting structure 1 is formed to exactly fit the lug 3 and the base 2 of the facing and is built up by first providing a partial backing member 8 which is a shallow boat-shaped member likewise cast, stamped or swedged, from gold.

The boat-shaped partial backing 8 is formed to provide a concave groove or slot to accommodate and exactly fit the convex lug 3 that extends from the base 2 of the facing. The groove formed in the partial backing 8 is under-cut as at 9 to receive the dovetailed lug 3 in interlocking relation, and this groove is likewise tapered longitudinally of the partial backing member, so that when the lug 3 is fitted into the groove by a rocking or sliding movement as indicated in Fig. 8, the lug will become fixed and locked in the partial backing 8 at the place where the backing 8 will be disposed exactly in the proper position relative to the margins of the facing.

As shown in Fig. 7, the partial backing 8 is convex on its bottom surface, and is made with just sufficient body to give it strength and rigidity, and the upper longitudinal margins are concaved to precisely fit the convex base of the facing l.

The purpose of the partial backing member 8 is to simplify the process of casting or forming the supporting cup member or bridge structure for the facing member I so that an exact fit between the supporting bridge structure and the facing will be had regardless of the skill of the operator or technician. This is of particular importance since it is intended that the facing members are to be standard molded replaceable elements and the groove in the bridge structure must therefore be of standard uniform shape in order that an accurate fit between the standard facing and the completed bridge structure can be had.

Through the use of the herein described improved occlusal facing and partial backing member, a sanitary bridge and the posterior part of a short bite removable bridge can be constructed quickly and successfully by simply carving the restoration pattern with the occlusal facing and the partial backing 8 in place, the restoration pattern being made of wax or other suitable material that can be readily molded and carved.

Thus, all that is necessary is to place the partial backing 8 in position on the base of the facing I, add wax to complete the backing structure pattern, and then cast in the usual manner as indicated by Figs. 10 and 11'. The casting mold is formed around the combined wax formation and partial backing 8 and then the wax is melted out, leaving simply a cavity in the mold ID in which the partial backing 8 is exactly and correctly positioned as shown in Fig. 10. Molten gold is then poured into the mold l0 and immediately embodies the partial backing 8, as shown in Fig. 11, as an integral part of the complete backing.

After casting, one or more completed backings, depending upon size of bridge, are assembled and soldered to the abutments of bridge. The

porting members 1, the insertion of the facings being accomplished by a rocking and sliding movement, as illustrated in Fig. 8, the narrow or leading end 5 of the lug 3being first inserted in the wide portion of the groove provided in the partial backing 8 and the facing being positively locked in the exact proper position by the cooperating and coacting relationship of the lug 3, and the dove-tailed groove in the partial backing 8. Thus the bridge is completed and ready for insertion in the patients mouth.

It will be seen that with a stock of standard facings and partial backing members it will be a relatively easy operation for a technician to construct the bridge work since the supporting cups are carved and completely molded about a properly positioned partial backing, so that a perfect fit is assured between the facing and the metal bridge structure.

As shown in Fig. 8, with the improved facing and partial backing combination, the bridge construction can be made so that its deepest portion will be at its center, the lower surface of the metal bridge tapering downwardly on both the buccal and lingual sides toward the center so as to reduce to a minimum the possibility of food becoming lodged and wedged in the space between the bridge and the gum ridge. In ordinary bridge construction, the lower surface of the bridge has portions that are parallel with the gum ridge and the thickness of the bridge in a transverse direction becomes greater toward the buccal side so that in many cases food becomes wedged between the bridge and the gum ridge.

The present improved construction not only obviates these objectionable features of ordinary bridge work, but provides the thickness at the very point where greatest strength is needed; namely, at the center of each artificial tooth in the complete restoration.

The herein described construction will provide a durable and beautiful sanitary bridge at the same time utilizing considerably less metal than ordinary constructions, and will leave sufficient space between the gum and the bridge for cleansing purposes, which cleansing may be readily accomplished because of the absence of any portions in or against Whic food might become wedged;

A particular advantage of the improved facing and partial backing combination is that the use of the facing eliminates the objectionable appearance of metal. Furthermore, considerable of the dentistsor technicians time ordinarily employed in the construction of a bridge is saved since the standard occlusal facing is already carved to anatomical form,.and the standard partial backings are preformed to exactly fit and receive the occlusal facing in exactly the proper relationship. The improved rocking lug arrangement also provides for more easy and perfect interlocking of the facing and the supporting structure. The improved construction saves precious metal to the extent of the volume of the facing, and in case of breakage of a facing a new facing of similar mold and shade can be easily inserted into the bridge construction with out necessitating removal of the bridge work from the patients mouth, such replacement of the broken facing being accomplished with the assurance that the new facing will fit in exactly the proper position.

Although but one specific embodiment of this invention is herein shown and described, it will be understood that details of the construction shown may be altered or omitted without departing from the spirit of this invention as. defined by the following claim:

I claim:

A bridge of the class described comprising end supporting parts adapted for dental mounting and a connecting body part integral with said end parts, in combination with a thin backing member set permanently in the face of said body part, and a thin discoidal porcelain occlusal facing renewably cemented to said backing member in a substantially horizontal position, which backing member is oblong crosswise of the bridge and somewhat crescent shaped and having its ends substantially sharp edged and flush with the horizontal occlusal edges of the bridge respectively, said facing having a convex crescent shaped dovetail lug on its bridge side, and said backing member having a corresponding concave groove in its outward side to receive the said facing interlockingly by a sliding and rocking movement.

MYRON I. LIFSCI-IUTZ. 

